Da marathon runner runs at a average speed of 5.33 meters per second for the first
73600 seconds and then at a speed of 5.00 meters per second for the next 4200
seconds. what is the average speed of the marathon runner in meters per second?
f
5.1 m/s
g
2.6 m/s
h
0.4 m/s
j 1.06 m/s

The average speed of the marathon runner is 5.15 meters per second

Explanation:

Lets revise the meaning of average speed

The average speed of an object is the total distance traveled by

the object divided by the time taken to cover that distance

A marathon runner runs at a average speed of 5.33 meters per second

for the first  3600 seconds

⇒ His speed = 5.33 m/s

⇒ For time = 3600 seconds

Then he runs at a speed of 5.00 meters per second for the next

4200  seconds

⇒ His speed is 5 m/s

⇒ For time 4200 seconds

Average speed = total distance ÷ total time

Lets find the total distance

Distance = speed × time

⇒ The 1st distance = 5.33 × 3600 = 19188 meters

⇒ The 2nd distance = 5 × 4200 = 21000 meters

⇒ Total distance = 19188 + 21000 = 40188 meters

Lets find the total time

⇒ Total time = 3600 + 4200 = 7800 seconds

⇒ Average speed = 40188 ÷ 7800 = 5.15 m/s

The average speed of the marathon runner is 5.15 meters per second

according to jean piaget, in what stage of cognitive development are children able to understand conservation task?

b. preoperational

just took it